High-aperture hydrolens with the remote entrance pupil is known (certificate of authorship SU1642426A1, published on 15.04.1991, bull. No. 14), composed of remote entrance pupil in front of the projection lens and six lenses sequentially arranged along the pathway of the optical radiation from the object to the image, the first and the third of the lenses are positive menisci, having the concave surfaces facing an object side, second lens is a negative meniscus, having the concave surface facing an object side, the forth and the fifth lenses are biconvex, and the sixth one is biconcave, where the fifth and the sixth lenses are cemented together.
This projection lens has the following advantages: a remote entrance pupil in front of the lens, satisfactory image size. However, its relative aperture size is not sufficient, and light distribution in an image is poor, insufficient image quality, as well as the condition of its application, that is the operation in finitely conjugates mode, that are placed to the aqueous media.
A projection lens with a remote entrance pupil is known from the invention patent (RU2225628C2, published on 10.03.2004), composed of four optical components, sequentially arranged along the pathway of the optical radiation from the object to the image, the first of which is negative power, having the concave surfaces facing an object side and comprising biconcave and biconvex lenses being cemented together, the second component is biconvex, the third is positive power, having the concave surfaces facing an image side, and comprising biconvex and biconcave lenses being cemented together, the forth one is negative meniscus, having the concave surfaces facing an object side.
The advantages of this projection lens are: large image size, small dimensions, a remote entrance pupil in front of the projection lens.
The disadvantages of this lens are: low ratio of brightness of the edge of the image against the brightness in the centre of the image, low size of relative aperture, the value of negative distortion that is insufficient for correction of positive distortion of X-ray image intensifier, operating of projection lens with an infinitely remote object, insufficient image quality.